Well according to the bluebook FAQ #1, there is no software that fully supports bluebook and it recommends manual intervention 
JurisM (which is developed by Frank Bennett @fbennett who made citeproc-js) modifications to CSL were folded into the CSL-M spec if I remember correctly and citeproc-rs (which is supposed to be a replacement for citeproc-js, and did get inputs from @fbennett) aims to support it:
https://citeproc-js.readthedocs.io/en/latest/csl-m/index.html
But citeproc-rs is really a tool for developers to build processors, not an end-user tool itself. I don’t know of any end-user tools yet. You could ask on the Zotero forums what the plan is to allow Zotero to use citeproc-rs with CSL-M extensions and whether this is enough?
I asked several years ago (Academic Bibliographies: support citeproc as an option during compile) for citeproc support added to Scrivener as this would enable Scrivener to add fully bibliography formatting to its repertoire with a minimal support burden to KB, but I don’t know whether there are enough academic users who would use it to justify this to L&L. If KB did choose the citeproc-rs engine to integrate, then CSL-M support would be possible directly.
Pandoc also has a highly compliant CSL (not CSL-M) engine (https://github.com/jgm/citeproc), and I wonder whether a Pandoc plugin could fill in the gaps between CSL and CSL-M, if so Pandoc does work perfectly with Scrivener. You could ask on the Pandoc google group, if you give very specific details of what bluebook requires.
Why anyone made such a difficult citation system is beyond me, and I’m thankful in Science our citation formatting is straight-forward! I would intuitively imagine that there has to be money to be made (how much would desperate lawyers pay!) for software that does support this robustly.